Oxidative sweetening with base and quaternary ammonium compound



United States Patent OXEDATKVE SWEETENING WHTH BASE AND QUATERNARYAMMGNIUM QQMPOUND Rolland G. Bowers, Perryshurg, Ghio, assignor to SunOil Company, Philadelphia, El a, a corporation of New Jersey No Drawing.Continuation of applications Ser. No. 137,717, Sept. 13, 1961, and Ser.No. 170,510, Feb. 1, 1962. This application Feb. 26, P263, Ser. No.261,16

13 Claims. (Cl. 2082ti6) This invention relates to sweetening sourhydrocarbon distillates, and more particularly to a manner of providingincreased sweetening rate.

It is known in the art to sweeten sour hydrocarbon distillates bycontact with phenylene diamine compounds in the presenceof an alkalinecatalyst. Such process is commonly referred to as inhibitor sweetening.The process is believed to involve oxidation of mercaptans todisulfides, by gaseous oxygen, catalyzed by the phenylene diaminecompound and the alkaline material.

In the known process, the rate of mercaptan conversion is sometimes notrapid enough for satisfactory results. According to the presentinvention, a novel man ner is provided of obtaining more rapidsweetening. This result is obtained by carrying out the process in thepresence of a quaternary ammonium nitrite or halide.

The quaternary ammonium nitrite or halide which is used in the processcontains at least one aliphatic or cycloaliph-atic radical having atleast 12 carbon atoms. Such radicals can advantageously be those whichare contained in naturally occurring fatty acids such as coconut oilfatty acids. It is known in the art to convert coconut oil fatty acidsto mixtures of amines, in which one or more of the alkyl radicalsoriginally attached to the carboxyl group of the fatty acid, iscontained in the amine. It is also known to convert such amines toquaternary ammonium nitrites or halides containing four alkyl groups, atleast one of which is the alkyl radical derived from the coconut oilfatty acids. Thus, for example, dicoco dimethyl ammonium nitrite orhalide contains two such alkyl groups and two methyl groups attached tothe nitrogen atom. The aliphatic or cycloaliphatic group or groupscontaining 12 or more carbon atoms can also be derived from othernaturally occurring fatty acid mixtures, or from individual fatty acids,or from naturally occurring cycloaliphatic acids such as petroleumnaphthenic acids or rosin. Usually the hydrocarbon radical will notcontain more than 24 carbon atoms, though greater numbers are suitablein some cases.

Examples of suitable quaternary ammonium nitrites and halides for useaccording to the invention include monococo trimethyl ammonium nitrite,dodecyl trimethyl ammonium nitrite, hexadecyl triethyl ammonium nitrite,dihexadecyl dimethyl ammonium nitrite, cetyl lauryl dimethyl ammoniumnitrite, dioleyl diethyl ammonium nitrite, din-aphthenyl dimethylammonium nitrite, diabietyl dimethyl ammonium nitrite, and thecorresponding halides, etc. Preferred nitrites are those containing oneor two, and more preferably one, alkyl radicals, each having 12 to 14carbon atoms, and two or three radicals each having 1 to 3 carbon atoms.Particularly preferred compounds are those containing alkyl radicalsderived from coconut oil acids.

The amount of nitrite or halide in the sweetening mixture is preferablyin the range from 0.001 to 1.0 weight percent based on hydrocarboncharge stock. Other amounts can be used in some cases; greater amountsare usually avoidedsince unnecessary for satisfactory results.

EJ54544 i atentecl Jan. 5, 1965 "ice The known phenylene diaminecompounds for use in inhibitor sweetening are generally suitable for useaccording to the invention. The most commonly used com pound isN,N-di-secondary-butyl-p-phenylene diamine. Other suitable phenylenediamine compounds include N,N'-di-isopropyl-p-phenylene diamine,N,N-di-secondary-amyl-p-phenylene diamine,N-isopropyl-N'-secondarybutyl-p-phenylene diamine,N-isopropyl-N-secondaryamyl-p-phenylene diamine,N-secondary-butyl-N'-secondary-amyl-p-phenylene diamine, etc. The amountof phenylene diamine compound employed is generally within theapproximate range from 0.0001 to 1.0 weight percent based onhydrocarbons, more preferably, 0.001 to 0.1 weight percent. However, anyamount known to be suitable for inhibitor sweetening can be used.

The alkaline material which is employed in the process according to theinvention is any alkaline material which is known for use in catalyzinginhibitor sweetening reactions. Examples of suitable alkaline materialsare the hydroxides of the alkali metals or alkaline earth metals,sodium, potassium, calcium, strontium, barium, etc., ammonia, andorganic basic compounds which are substantially insoluble inhydrocarbons, e.g., polyamines such as diethylene triamine, triethylenetetramine, tetraethylene pentamine, 1,2-diaminopropane,1,3-diaminobutane, 1,3,5- triaminopentane, 1,3,6-triaminohexane,1,3,5,7-tetraminoheptane, etc., aminoalcohols including aminoethanol,diaminopropanol, triaminobutanol, tetraminopentanol, etc. and quaternaryammonium compounds including tetramethyl ammonium hydroxide, tetraethylammonium hydroxide, tetrapropyl ammonium hydroxide, tetramethyl ammoniummethoxide, tetramethyl ammonium ethoxide, tetraethyl ammonium ethoxide,etc. Mixtures of alkaline materials, e.g. of ammonia and sodiumhydroxide, etc., can be employed.

The amount of alkaline material which is employed in the process of theinvention is preferably within the approximate range from 0.01 to 5weight percent, although any amount known to be suitable for use inoxidative sweetening operations can be employed.

The temperature conditions of the sweetening operation according to theinvention can be those which are employed in the conventional sweeteningoperations, eg in the range from 50 F. to F., though other temperaturescan be employed.

Agitation of the sweetening mixture promotes the conversion ofmercaptans. Agitation can be provided only at the beginning of thesweetening operation, or irregularly during the operation, or it can beprovided periodically or continuously during the operation. In somecases at least, the presence of the nitrite or halide according to theinvention reduces the extent of the agitation needed to providesatisfactory sweetening rate.

Molecular oxygen is required for the sweetening operation. Frequently,petroleum distillates normally contain sufiicient dissolved oxygen toobtain substantial sweetening. Additional oxygen can be supplied,regularly or irregularly, if needed.

The process according to the invention is applicable generally to thosemercaptan-containing petroleum frac tions, such as gasoline, naphtha,kerosine and fuel oil fractions, which are known to be susceptible tooxidative sweetening with alkaline catalyst; A typical charge stock is a62 API, 400 F. endpoint, catalytically cracked and caustic-pretreatedgasoline containing about 0.01 weight percent mercaptan sulfur, but theapplicability of the invention to other known charge stocks foroxidative sweetening processes will be readily apparent.

The following reaction mixture is prepared:

Cc. Petroleum fuel containing 0.0069 Wt. percent mercaptans n 400 20 B.caustic soda 10 N,N'-dibutyl phenylene diamine.

Monococo trimethyl ammonium nitrite.

The amounts of the latter two components are equivalent to 5 pounds ofthe diamine per 1000 barrels of fuel, and pounds per 1000 barrels offuel of a mixture of the nitrite and isopropanol, containing 50% of thenitrite.

The mixture is agitated for one hour at room temperature, then allowedto stand for 5 hours. 100 cc. of air are then injected, and the mixtureshaken for minutes. The mixture is then allowed to stand. The followingtable shows the mercaptan contents at the indicated times, measured fromthe initial mixing. For comparison, results are shown for identicaloperation, with the monococo trimethyl ammonium nitrite omitted.

Wt. percent Mereaptan- Monococo trimethyl am- Hours monium nitritePresent Absent These data show the acceleration in rate of mercaptanconversion obtained by the use of the monococo trimethyl ammoniumnitrite.

' Example 2 The latter two components are added as a mixture withaqueous isopropanol, the solution containing of the soya chloride and25% of the dicoco chloride. The mixture is used in amount equivalent toone pound of mixture per 1000 barrels of gasoline.

The soya trimethyl ammonium chloride is a compound similar to themonococo trimethyl ammonium chloride disclosed previously, butcontaining the hydrocarbon radical of soybean fatty acids in place ofthe hydrocarbon radicalor coconut oil fatty acids.

The reaction mixture is blown with air for seconds, then shaken for 30minutes and allowed to stand. The reaction mixture is cloudy immediatelyafter shaking, but clear after 2 hours. The following table shows themercaptan contents at the indicated times, measured from the initialmixing. For comparison, results are shown for identical operation, withthe mixture of soya trimethyl ammonium chloride and dicoco dimethylammonium chloride omitted.

The copper dish gum of the gasoline after 24 hours is 11 mg./100 ml. inthe case Where the quaternary chlorides are present, and 19 mg./100 ml.in the case where they are absent.

4 Example 3 The procedure of Example 2 is repeated, using however amixture, with aqueous isopropanol, of dicoco dimethyl ammonium chloride(constituting 75% of the mixture) as sole quaternary chloride, in placeof the mixture containing two quaternary chlorides as used in Example 2.The following results are obtained:

Wt. percent Mercaptan Hours Quaternary Quaternary chlorides chloridespresent absent Copper dish gum after 24 hours is 14 mg./ ml. wherequaternary chloride is present, 19 mg./100 ml. where absent.

Example 4 The procedure of Example 2 is repeated, using however adifferent gasoline, containing initially 0.0029 wt. percent mercaptan,and using N,N'-dibutyl phenylene diamine, in amount equivalent to 5pounds thereof per 1000 barrels of gasoline in addition to the othercomponents of the reaction mixture; the quaternary chloride mixture withaqueous isopropanol is used in amount equivalent to 5 pounds per 1000barrels of gasoline, rather than 1 pound per 1000 barrels as in Example2; Comparison is made with another reaction mixture containing the abovephenylene diamine derivative but lacking the two quaternary chlorides.The following results are obtained:

Wt. percent Mereaptan Hours Quaternary Quaternary chlorides chloridespresent absent 0. 0006 0. 0011 0. 0001 0. 0007 nil 0. 0005 Copper dishgum after 24 hours is 7 mg./100 ml. where quaternary chlorides arepresent, 13 where absent.

Example 5 Example 4 is repeated substituting the dicoco derivative ofExample 3 for the two quaternary chlorides used in Examples 2 and 4.The'following results are obtained:

Copper dish gum after 24 hours is 9 mg./ 100 ml. where quaternarychlorides are present, 13 mg./100 ml. where absent.

Generally similar results to those obtained in the preceding examplesare obtained using other quaternary ammonium nitrites or halides,phenylene diamine agents and alkaline materials such as thosespecifically disclosed previously. Halides contemplated for use includebromides and iodides as well as chlorides, though the latter arepreferred.

This application is a continuation of application Serial No. 137,717,filed September 13, 1961, now abandoned, which was acontinuation-in-part of application Serial No. 861,464, filed December23, 1959, now abandoned. This application is also a continuation ofapplication Serial No. 170,510, filed February 1, 1962, now abandoned.

The invention claimed is:

1. Process for reducing mercaptan content of hydrocarbons whichcomprises contacting hydrocarbons containing mercaptans with an alkalinecatalyst and a quaternary ammonium nitrite containing at least onehydrocarbon radical selected from the group consisting of aliphatic andcycloaliphatic radicals and having at least 12 carbon atoms, in thepresence of oxygen and a phenylene diamine sweetening agent.

2. Process according to claim 1 wherein said nitrite contains threealkyl groups each having 12 to 14 carbon atoms and one alkyl grouphaving 1 to 3 carbon atoms.

3. Process according to' claim 1' wherein said nitrite is monococotrimethyl ammonium nitrite.

4. Process according to claim 1 wherein the amount of alkaline catalystis in the range from 0.01 to 5 weight percent based on hydrocarbons.

5. Process according to claim 1 wherein the amount of said nitrite is inthe range from 0.001 to 1.0 weight percent based on hydrocarbons.

6. Process according to claim 1 wherein the amount of said agent is inthe range from 0.0001 to 1.0 weight percent based on hydrocarbons.

7. Process for reducing mercaptan content of hydrocarbons whichcomprises contacting hydrocarbons containing mercaptans with an alkalinecatalyst and a quaternary ammonium halide containing at least onehydrocarbon radical selected from the group consisting of aliphatic andcyclojaliphatic radicals and having at least 12 carbon atoms, in thepresence of oxygen. 1

8. Process according to claim 7 wherein said halide contains 2 to 3alkyl groups each having 12 to 14 carbon atoms and 1 to 2 alkyl groupshaving 1 to 3 carbon atoms.

9. Process according to claim 7 wherein said halide is dicoco dimethylammonium chloride.

10. Process according to claim 7 wherein the amount of alkaline catalystis in the range from 0.01 to 5 weight percent based on hydrocarbons.

11. Process according to claim 7 wherein the amount of said halide is inthe range from 0.001 to 1.0 weight percent based on hydrocarbons.

12. Process according to claim 7 wherein the contacting is in thepresence of a phenylene diamine sweetening agent in amount in the rangefrom 0.0001 to 1.0 weight percent based on hydrocarbons.

13. Process for reducing mercaptan content of hydrocarbons whichcomprises contacting hydrocarbons containing mercaptans with an alkalinecatalyst and a quaternary ammonium compound containing at least onehydrocarbon radical selected from the group consisting of aliphatic and;cycloaliphatic radicals and having at least 12 carbon atoms, in thepresence of oxygen, said compound being selected from the groupconsisting of quaternary ammonium nitrites and quaternary ammoniumhalides.

References Cited in the file of this patent UNITED STATES PATENTS

13. PROCESS FOR REDUCING MERCAPTAN CONTENT OF HYDROCARBONS WHICHCOMPRISES CONTACTING HYDROCARBONS CONTAINING MERCAPTANS WITH AN ALKALINECATALYST AND A QUATERNARY AMMONIUM COMPOUND CONTAINING AT LEAST ONEHYDROCARBONRADICAL SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC ANDCYCLOALIPHATIC RADICALS AND HAVING AT LEAST 12 CARBON ATOMS, IN THEPRESENCE OF OXYGEN, SAID COMPOUND BEING SELECTED FROM THE GROUPCONSISTING OF QUATERNARY AMONIUM NITRITES AND QUATERNARY AMMONIUMHALIDES.